Against half guards in a Leeward Island? (7)
I believe the answer is:
antigua
'a leeward island?' is the definition.
(I've seen this in another clue)
'against half guards' is the wordplay.
'against' becomes 'anti' (prefix meaning against).
'half' means to take half the letters.
'guards' cut in half is 'gua'.
'anti'+'gua'='ANTIGUA'
'in' is the link.
(Other definitions for antigua that I've seen before include "former British possession" , "warm island" , "Caribbean island linked with Barbuda" , "One of the Leeward Islands" , "Largest of Leeward Is." .)